The actual Tweet:

    we had a significant issue in ChatGPT due to a bug in an open source library, for which a fix has now been released and we have just finished validating. a small percentage of users were able to see the titles of other users’ conversation history. we feel awful about this.

Imagine if the bug was caused by closed-source library. Then maybe he'd have posted

    we're having a significant issue in ChatGPT due to a bug in a proprietary, closed-source library. Unfortunately the developers have not responded to our report, and as we do not have access to the code, we cannot fix the bug ourselves. we feel awful about this. perhaps this is why OSS is so widely-accepted in the software engineering community, and many of the widely-used libraries of today are open source.